This invention concerns a fuel gauge unit to provide a visual indication of the quantity of fuel in a fuel tank fixed on the top of a small multi-purpose single-cylinder engine.
FIGS. 3 and 4 show the configuration of a prior art fuel gauge unit which is used in small multi-purpose singlecylinder engines (hereinafter called simply xe2x80x9cenginesxe2x80x9d). FIG. 3 is a plan view showing the main components; FIG. 4 is a cross section taken along line Axe2x80x94A in FIG. 3.
In FIGS. 3 and 4, 1 is the fuel tank installed on top of the engine; it is made of synthetic resin, i.e. plastic, and welded. On the top of the fuel tank 1 are a fuel inlet, which has a cap 2 and a fuel filter 3, and a fuel gauge unit 4. The fuel gauge unit 4 comprises cover plate 6, which is made of a flat material; a gauge body 7, formed from molded resin, which has a transparent window 7a; a guide cylinder 11, which has a long hole in its bottom to guide the arm of indicator 12a; a cylindrical packing 8, which seals the guide cylinder; a shaft 9, which extends through both the aforesaid gauge body 7 and the guide cylinder 11 and holds both in place: and an indicator bearing 12, which is supported by the shaft 9 so that it is free to rotate, and to which are fixed the indicator 12a and the float 12b, which sits on the surface of the fuel in fuel tank 1.
In this engine, when fuel gauge unit 4 is mounted to the fuel tank 1, it is pressed into the fuel tank with packing 8 around and in front of it. Cover plate 6 is placed on top of the gauge body 7. Tabs provided in appropriate places on the mounting surface of fuel tank 1 engage in holes in the cover plate 6. While plate 6 is being pressed onto the upper surface of gauge body 7, the tabs are heated to melt them into place. (Alternatively, holes may be provided in appropriate places on the mounting surface of the fuel tank 1, and cover plate 6 may be fixed in place by means of screws or rivets.)
With the aforesaid fuel gauge unit 4, when the fuel tank 1 is full, float 12b will float and indicator bearing 12 will rotate. Indicator 12a, which is attached to the bearing 12, will move in the horizontal direction and point to the xe2x80x9cFxe2x80x9d on transparent window 7a, which indicates that the fuel tank is full. As the engine uses the fuel, indicator 12a will move in the downward direction in FIG. 3, and when the fuel tank is empty, indicator 12a will point to the xe2x80x9cExe2x80x9d on transparent window 7a, which indicates that the fuel tank is empty. In other words, the fuel gauge unit 4 allows the user to visually ascertain whether there is fuel in fuel tank 1 and how much fuel there is.
As can be seen in FIGS. 3 and 4, fuel gauge unit 4 must be cylindrical so that it can be sealed against the fuel, and the seal is constructed using packing 8 or O rings. Thus, when the fuel gauge unit 4 is installed on fuel tank 1, there is no way to control the direction of rotation of the gauge with respect to the fuel tank.
This is why the prior art fuel gauge shown in FIGS. 3 and 4 has projections in given positions along its circumference, so that the gauge body 7 is asymmetrical with respect to its center line. This requirement drives up the cost of fuel gauge unit 4.
Furthermore, because the user must visually ascertain the level of the fuel in fuel tank 1, the prior art fuel gauge must have a fuel scale (the aforesaid xe2x80x9cFxe2x80x9d or xe2x80x9cExe2x80x9d) engraved or printed on the top of gauge body 7 or a separate plate with a scale must be made and installed. This drives up the cost of constructing the fuel gauge.
The object of this invention is to provide a fuel gauge for a fuel tank with a simple configuration that will make it easy to control the rotational position of the gauge when it is fixed to the fuel tank, that will have a simple and inexpensive fuel scale, and that will allow the fuel level to be determined with certainty.
To solve the problems described above, a first preferred fuel gauge embodiment for a fuel tank of the sort in which a bearing for an indicator connected to a float that sits atop the fuel in the fuel tank is supported by the gauge so that it is free to rotate. When the bearing rotates, the indicator connected to the bearing moves back and forth horizontally. The position of the indicator is correlated with a fuel scale, so that the quantity of fuel in the fuel tank can be ascertained visually. This fuel gauge is distinguished by the fact that there is a transparent window in the upper portion of the aforesaid gauge which protrudes upward, and by the fact that there is a hole in the cover plate affixed to the fuel tank in which the protruding portion of the gauge fits. The surface of the protruding portion and the hole in which it fits may be square or elongated.
A second preferred fuel gauge embodiment according to the invention is a fuel gauge described as the foregoing first preferred embodiment, but in which the fuel scale is provided on the cover plate, so that it corresponds to the position of the fuel indicator as viewed through the window.
With this invention, when the fuel gauge is installed on the fuel tank, the protruding portion of the gauge fits into the hole in the cover plate. The protruding portion and the hole together form a rotation stopper. When they are fitted together, the rotational position of the gauge, that is, of the fuel gauge with respect to the fuel tank (or rather to the cover plate), is determined by itself, and they function as a rotation stopper.
With this invention, then, there is no need to create protuberances or asymmetries in the gauge so that its rotational position can be determined, as is the case with prior art gauges. When the protruding portion is fitted into the hole, the rotational position of the gauge is determined, and a reliable rotation stopper is created.
Because the rest of the protruding portion of the gauge, i.e. the part of it not occupied by the window, is masked by the cover plate, it is easy to read the indicator, which improves the handling qualities of the gauge.